Protein therapeutics, such as antibodies, cytokines, growth factors and vaccines, are important therapeutics for the treatment of a variety of diseases including, for example, cancer, diabetes and cardiovascular diseases. This class of protein therapeutics has been developed rapidly in the global pharmaceutical industry over the last few years. Protein therapeutics have the advantages of high specificity and potency relative to small molecule drugs. Nonetheless, the use of protein therapeutics is limited as a result of their intrinsic instability, immunogenicity and short half-life.
To address these limitations, there are generally two approaches: one is genetic fusion of the therapeutic protein, and the other is use of engineered carriers to deliver protein therapeutics. With engineered carriers, proteins are loaded by either encapsulation/adsorption or conjugation. Encapsulation or adsorption of proteins in/onto liposomes or nanoparticles is typically inefficient. Conjugation of proteins typically reduces their bioactivity. Thus, both approaches are problematic.